Potts2030, I think that it may be better to look at the work, rather than the tail lift itself: if an employee falls from the height they are working from, how bad will the injury be? How likely is the fall? If the resulting risk is significant it needs to be controlled. Of course the lifting mechanism itself and all the possibilities of injury from trapping etc can be considered at the same time, along with any manual handling issues present.

There have been many incidents of drivers falling from height whilst loading etc and resulting in nasty, disabling injuries although most of those that I recall have been from wagon beds or the top of the load, not a tail-lift. Maybe other contributors have specific knowledge.

Working in the rear of a vehicle near the edge (at whatever the floor height is obove ground level) is just the same as working on a tail lift. I have never seen any vehicle drivers wearing safety harness and tethered to the vehicle while doing general loading / unloading etc. I think for this consideration of work at heights the concept of Reasonably practicable should be brought into play.